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  <h1>Source code for pyamp.patterns.interfaces.finalFunctionsMeta</h1><div class="highlight"><pre>
<span class="c"># Copyright 2012 Brett Ponsler</span>
<span class="c"># This file is part of pyamp.</span>
<span class="c">#</span>
<span class="c"># pyamp is free software: you can redistribute it and/or modify</span>
<span class="c"># it under the terms of the GNU General Public License as published by</span>
<span class="c"># the Free Software Foundation, either version 3 of the License, or</span>
<span class="c"># (at your option) any later version.</span>
<span class="c">#</span>
<span class="c"># pyamp is distributed in the hope that it will be useful,</span>
<span class="c"># but WITHOUT ANY WARRANTY; without even the implied warranty of</span>
<span class="c"># MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the</span>
<span class="c"># GNU General Public License for more details.</span>
<span class="c">#</span>
<span class="c"># You should have received a copy of the GNU General Public License</span>
<span class="c"># along with pyamp.  If not, see &lt;http://www.gnu.org/licenses/&gt;.</span>
<span class="sd">&#39;&#39;&#39;The finalFunctionsMeta module contians classes which provide the</span>
<span class="sd">ability to declare specific functions of a class to be &#39;final&#39;, which</span>
<span class="sd">means that an Exception will be raised in the event that a subclass</span>
<span class="sd">tries to override the functionality of those functions.</span>

<span class="sd">Here is an example of using the classes in this module::</span>

<span class="sd">    # First define the metaclass that defines the list of final functions</span>
<span class="sd">    class FinalMeta(FinalFunctionsMeta):</span>
<span class="sd">        finalFunctions = [&quot;__del__&quot;]</span>

<span class="sd">    # Now define the base class which forces all child classes to use the</span>
<span class="sd">    # correct metaclass</span>
<span class="sd">    class Parent(FinalFunctionsParentBase):</span>
<span class="sd">        requiredMetaclass = FinalMeta</span>

<span class="sd">        def __init__(self):</span>
<span class="sd">            FinalFunctionsParentBase.__init__(self)</span>

<span class="sd">    # Finally, define the child class and override a few of the</span>
<span class="sd">    # parents functions</span>
<span class="sd">    class Child(Parent):</span>
<span class="sd">        __metaclass__ = FinalMeta</span>

<span class="sd">        # This function can be overridden</span>
<span class="sd">        def __init__(self):</span>
<span class="sd">            Parent.__init__(self)</span>

<span class="sd">        # This function CANNOT be overridden</span>
<span class="sd">        def __del__(self):</span>
<span class="sd">            Parent.__del__(self)</span>

<span class="sd">    # This will throw an Exception indicating that __del__ cannot be</span>
<span class="sd">    # overridden by the Child class!</span>
<span class="sd">    c = Child()</span>

<span class="sd">&#39;&#39;&#39;</span>
<span class="kn">from</span> <span class="nn">pyamp.util</span> <span class="kn">import</span> <span class="n">isFunction</span>
<span class="kn">from</span> <span class="nn">pyamp.patterns.interfaces</span> <span class="kn">import</span> <span class="n">RequiredProperties</span>
<span class="kn">from</span> <span class="nn">pyamp.exceptions</span> <span class="kn">import</span> <span class="n">FinalFunctionError</span><span class="p">,</span> <span class="n">InvalidPropertyValueError</span>


<div class="viewcode-block" id="FinalFunctionsMeta"><a class="viewcode-back" href="../../../../_generated/pyamp_patterns_interfaces_finalFunctionsMeta.html#pyamp.patterns.interfaces.finalFunctionsMeta.FinalFunctionsMeta">[docs]</a><span class="k">class</span> <span class="nc">FinalFunctionsMeta</span><span class="p">(</span><span class="nb">type</span><span class="p">):</span>
    <span class="sd">&#39;&#39;&#39;The FinalFunctionMeta class is a metaclass which provides the ability</span>
<span class="sd">    to define a list of functions that should not be allowed to be overridden</span>
<span class="sd">    by classes which use this metaclass.</span>

<span class="sd">    &#39;&#39;&#39;</span>
    <span class="n">finalFunctions</span> <span class="o">=</span> <span class="p">[]</span>

    <span class="k">def</span> <span class="nf">__new__</span><span class="p">(</span><span class="n">mcs</span><span class="p">,</span> <span class="n">className</span><span class="p">,</span> <span class="n">parents</span><span class="p">,</span> <span class="n">attributes</span><span class="p">):</span>
        <span class="sd">&#39;&#39;&#39; &#39;&#39;&#39;</span>
        <span class="k">for</span> <span class="n">name</span><span class="p">,</span> <span class="n">attribute</span> <span class="ow">in</span> <span class="n">attributes</span><span class="o">.</span><span class="n">iteritems</span><span class="p">():</span>
            <span class="k">if</span> <span class="n">name</span> <span class="ow">in</span> <span class="n">mcs</span><span class="o">.</span><span class="n">finalFunctions</span> <span class="ow">and</span> <span class="n">isFunction</span><span class="p">(</span><span class="n">attribute</span><span class="p">):</span>
                <span class="k">raise</span> <span class="n">FinalFunctionError</span><span class="p">(</span><span class="n">className</span><span class="p">,</span> <span class="n">name</span><span class="p">)</span>

        <span class="k">return</span> <span class="nb">type</span><span class="o">.</span><span class="n">__new__</span><span class="p">(</span><span class="n">mcs</span><span class="p">,</span> <span class="n">className</span><span class="p">,</span> <span class="n">parents</span><span class="p">,</span> <span class="n">attributes</span><span class="p">)</span>

</div>
<div class="viewcode-block" id="FinalFunctionsParentBase"><a class="viewcode-back" href="../../../../_generated/pyamp_patterns_interfaces_finalFunctionsMeta.html#pyamp.patterns.interfaces.finalFunctionsMeta.FinalFunctionsParentBase">[docs]</a><span class="k">class</span> <span class="nc">FinalFunctionsParentBase</span><span class="p">(</span><span class="nb">object</span><span class="p">,</span> <span class="n">RequiredProperties</span><span class="p">):</span>
    <span class="sd">&#39;&#39;&#39;The FinalFunctionsParentBase provides a base class which provides the</span>
<span class="sd">    ability to define final functions in the base class. This will prevent any</span>
<span class="sd">    subclasses from overloading these specific, i.e., final, functions.</span>

<span class="sd">    This class provides the ability to specify the specific metaclass that</span>
<span class="sd">    **must** be defined for all subclasses of this base class. The metaclass</span>
<span class="sd">    chosen should be a subclass of the :class:`.FinalFunctionsMeta` metaclass</span>
<span class="sd">    which defines the list of final functions and keeps them from being</span>
<span class="sd">    overridden.</span>

<span class="sd">    &#39;&#39;&#39;</span>
    <span class="n">requiredMetaclass</span> <span class="o">=</span> <span class="bp">None</span>

    <span class="k">def</span> <span class="nf">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
        <span class="sd">&#39;&#39;&#39;Create the FinalFunctionsParentBase class.&#39;&#39;&#39;</span>
        <span class="c"># Set the required metaclass, only if one is provided</span>
        <span class="k">if</span> <span class="bp">self</span><span class="o">.</span><span class="n">requiredMetaclass</span> <span class="ow">is</span> <span class="ow">not</span> <span class="bp">None</span><span class="p">:</span>
            <span class="bp">self</span><span class="o">.</span><span class="n">_RequiredProperties</span> <span class="o">=</span> <span class="p">[(</span><span class="s">&quot;__metaclass__&quot;</span><span class="p">,</span>
                                         <span class="bp">self</span><span class="o">.</span><span class="n">requiredMetaclass</span><span class="p">)]</span>
        <span class="n">RequiredProperties</span><span class="o">.</span><span class="n">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">)</span></div>
</pre></div>

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